Question: Simplify the following expression: $q = \dfrac{3r}{4} - \dfrac{r}{6}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $6$ $\lcm(4, 6) = 12$ $ q = \dfrac{3}{3} \cdot \dfrac{3r}{4} - \dfrac{2}{2} \cdot \dfrac{r}{6} $ $q = \dfrac{9r}{12} - \dfrac{2r}{12}$ $q = \dfrac{9r -2r}{12}$ $q = \dfrac{7r}{12}$